0=x^2+15x+56

Solution for 0=x^2+15x+56 equation:

0=x^2+15x+56

We move all terms to the left:

0-(x^2+15x+56)=0

We add all the numbers together, and all the variables

-(x^2+15x+56)=0

We get rid of parentheses

-x^2-15x-56=0

We add all the numbers together, and all the variables

-1x^2-15x-56=0

a = -1; b = -15; c = -56;
Δ = b2-4ac
Δ = -152-4·(-1)·(-56)
Δ = 1
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1}=1$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-1}{2*-1}=\frac{14}{-2}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+1}{2*-1}=\frac{16}{-2}
=-8
$